Pulse transmission system



NW 1129 3%@- N. E. LINDENBLAD 2 PULSE TRANSMISSION SYSTEM Filed May 1,3.942 l Sheets-Sheet l I T lg m w. 6

7 I Sou/@c5 L i 6 f7 WW2-g v 4 BNVENTOR /M/Yfm/ ATTORNEY Nmn M, i946. N.E. LINDENBLAD PULSE TRANSMISSION SYSTEM Filed May l, 1942 4SheebS-Shee'l 2 Homer SPAR/f GAP NW10 ma E94@ N. E. UNDENBLAD2941-3131934@ PULSE TRANSMISSION SYSTEM I Filed May l, 1942 4Sheets-Sheet 5 LINDENBLAD Z-Mf@ PULSE TRANSMI SS ION SYSTEM Filed May 1,1942 4 Sheets-sheet 4 Patented Nov. 12, 1946 PULSE TRANSMISSION SYSTEMNils E. Lindenblad, Port Jeierson, N. Y., assignor to Radio Corporationof America, a corporation of Delaware Application May 1, 1942, SerialNo. 441,311

(Cl. Z50-36) 10 Claims.

This invention relates to improvements in bstacle detection radiosystems,

It is known in obstacle detection radio systems (sometimes referred toas radio locators) to ernploy a transmitter for transmittingperiodically repeated radio wave pulses of extremely short duration, anda receiver for receiving the pulses which are reflected by the obstacleto be detected. Such systems preferably employ directive antennas andother expedients for both transmitter and receiver by means of which theindications are conined to objects lying within a narrow range ofangles. The antennas are sometimes given a continuous motion to scan acertain range of solid angles somewhat after the fashion of scanning ateievision image and these antennas are linked to a potentiometer whichcontrols the voltage on the horizontal deection plates of anoscilloscope. 1n order to produce the radio wave pulses, it has beenproposed to excite periodically the osciliator of the transmitterthrough a spark gap switching device which is in series with theosciilator and the charging voltage source and to which is supplied atperiodic intervals a voltage of sufficient value to break down the gap.

One diiiiculty experienced with the aforesaid known systems has been dueto the trailing efiects caused by insufficient deionization of the sparkgap. as a result of which the carrier or radio wave pulses from theoscilla-tor are not as sharply defined as desired. This trailingcondition occurs because an undesired continuing arc in the spark gapcauses a current to flow through the oscillator to produce a continuedoutput from the oscillator. This continued output from the oscillator isof less intensity than that of the pulse produced during the early partof the discharge.

The present invention provides a system by means of which an undesiredcontinuing arc, due to insufiicient deionization of the spark gap, hasno effect on the oscillator oi the transmitter.

Among the features which contribute to the improved system of thepresent invention are the following: The rotary spark gap switchingdevice having a multiplicity of electrodes in spaced series relation forimproving the accuracy of the firing and the speed of disruption, thecompact transmission line, the circuit for assuring a sharp break in thedischarge across the spark gap, the circuit for preventing trailingeffects in the oscillator despite insuiicient deionization of the sparkgap, and the circuit for obtaining the necessary high pulse voltage forthe oscillator from a relatively low voltage alternating current source.

Other features and objects of the present invention will appear from areading of the following description, which is accompanied by drawingswherein the same parts are labeled with the same reference characters.

Figs. l, 2, 3, 4, 5 and 6 show different embodiments of the presentinvention for producing sharply defined periodically repeated radio wavepulses;

Fig, la, shows, in perspective, the novel compact transmission linearrangement which can be employed in the circuits of Figs. l to 4,inclusive;

Fig. lb is a cross-sectional view of the compact line of Fig. la alongthe line b-b;

lc shows a perspective View of the improved rotary spark gap switchingdevice of the invention;

Figs, 7 and 7a illustrate diagrammatically an improved form of choppercircuit which can be used in place of corresponding parts of Figs. 4, 5and 6 for converting energy obtained from a low direct current voltagesource to pulses of high voltage;

Fig. 8 is a modification of my improved chopper circuit for use in moregeneral applications; and

Fig, 9 shows the arrangement of Fig. 1 employing the articial line ofFig. la and the rotary spark gap of Fig. 1c.

Referring to Fig. 1 in more detail, there is shown one embodiment of theinvention for producing sharp, periodically repeated radio wave pulses.The oscillator for producing ultra short waves below one meter in length(preferably of the order of ten centimeters) is representedconventionally by box l. This oscillator may be any suitabie device, butis preferably a magnetron of the type shown and described, for example,in Hansell Patent 2,217,745, granted October 15, 1940. The anode ofmagnetron I is shown connected to ground, while the cathode is shownconnected to one stationary electrode 2 of a rotary spark gaparrangement 3. For certain conditions of operation, the cathode andanode connections as shown) can be reversed. The other stationaryelectrode li of the rotary spark gap is connected to one end i of atransmission line 'IL of predetermined length, to which is alsoconnected, through a high resistance B, a source of continuous directcurrent charging voltage 5. Line TL is open at the other end 3 in orderto enable the reflection therefrom, with a desired polarity, of a pulseof voltage initiated at the end nearest the spark gap. The oscillator i(which is the load for the line TL) has a resistance or impedance,during operation, equal to the characteristic impedance of the line TL.

A suitable antenna 9, preferably a directive antenna such as a dipole inthe focus of a parabolcid reilector, is coupled to the output of theoscillator l for radiating the radio wave pulses toward the object to bedetected.

In the operation of Fig. 1, the line TL is charged to potential -l-Efrom the direct current source 5 through the high resistance 6. When thecharge on line TL reaches a potential equal or slightly in excess of thebreak-down potential across the rotary spark gap, it discharges throughthe spark gap and the load l which matches the impedance of the line TLand as a result of which the potential across the conductors of coaxialline TL at terminal l' drops to a value equal to one-half the potentialof the charge. This means that a wave is initiated at the terminal 'i ofa potential opposite to that of the charging potential and having avalue equal to half that of the charging potential. vThis initiatedwave, ahead of which the potential is still +E and behind which it islit/2, travels down the length of the line TL to its other end 8, whereit is reflected back as a wave ahead of which the potential is E/2 andbehind which it is' zero. Thus, when the reflected wave returns toterminal 1 where there still remains a voltage of one-half E sustainingthe discharge, it reduces the sustaining voltage to zero. A constantdischarge has thus been maintained from the time the spark gap brokedown until the arrival of the reiiected wave. from another point ofview, it can be shown that a voltage 1/zll across the load (oscillator)will deliver to the load in the time required for a pulse to travel oneround trip on the line an amount of energy exactly equal to the totalelectrostatic energy stored in the line by the potential E. It can thusbe seen that the total phenomenon involved is equivalent to splittingthe charging potential in half and obtaining a discharge period the timeof which is twice as long as the wave traversed in one direction of theline. The length of line TL thus determines the time duration of thedischarge or direct current pulse applied to the oscillator to make itmomentarily operative to produce a carrier wave pulse. Thus, if'the linehas a length corresponding to the wave travel of half a microsecond, thepulse obtained from this line will have a duration of a Wholemicrosecond.

Now,'if the load l is a magnetron oscillator which requires the voltagefrom the line TL to run it, it will be obvious that it will oscillateonly during the application of voltage pulses from the line. Because theoscillator functions momentarily, it is possible to obtain a higheroutput than during a normal or continuous steady state. We thus apply amuch higher voltage than normally employed by a magnetron electrode butfor a very short period of time, and take out from the oscillator ashort wave at high power. As an example, with 20,000 volts appliedrtothe input of the line TL as a continuous charging voltage from thesource 5 (which can bea rectier) we may get an output from theoscillator of about 20 kw. at a frequency of 300 megacycles (10 cm.) foran interval of about one microsecond The radio wave pulses from theoscillator are spaced apart in time an amount which is large compared tothe time of each pulse.e FOX Looking at it 4 periodically repeatedpulses of one microsecond length, the interval between pulses can be ashigh as 500 microseconds.

The resistance E inserted between the direct current source and thepulse line TL should have a value much greater than the characteristicimpedance of the line TL or of the load resistance, so that when therush of current produced by the act of discharging the line TL is over,there is not enough flow from the direct current source 5 to maintainthe spark. By using a quenched spark gap, or a rotary spark gap, or onehaving an air-blast, the resistance 6 may be permitted to have a smallervalue than would be the case if the spark gap were constituted merely bya pair of spaced electrodes. Under all circumstances, the value ofresistor should be considerably greater than the characteristicimpedance of the line TL and the load resistance.

Accordance to the invention, it is preferred that the rotary spark gaparrangement be of the type illustrated in Fig. 1c, wherein use is madeof a plurality of spark gaps in series. This rotary gap arrangementcomprises a rotating insulating disc lil having a plurality of studs orelectrodes 'il located in a circle near its periphery, each of thesestuds extending through the disc. Two pairs of stationary electrodes l2,'l2 and 13, 13, respectively, are placed on one side of the disc and onthe arc of a circle having the same radius as the circle of the rotatingelectrodes. These stationary electrodes are suitably spaced apart fromeach other the same distance as are the electrodes on the rotary disc,the electrodes of each pairvbeing connected tog-ether. On the oppositeside of the disc l@ there are located stationary electrodes "lli, 15,'i5 and l5, also on an arc of a circle having the same radius and axisas the circle of the rotating electrodes. Electrodes 15, 'E5 areconnected to each other, while electrode 'Hl is connected to line TL andelectrode 'i5 connected to the load (in this case the magnetronoscillator). The rotary electrodes ll, 1I are spaced apart from thestationary electrodes to provide small gaps therebetween. In oneposition of the disc, it will be evident that there will be a Vdischargepath through the rotary spark gap `'system over a path including inseries the electrodes 74, 1l, l2, l2, 7l, l5, l5, li, i3, 13, H and l.The distances between the rotary and stationary electrodes are nowconsiderably smaller than would be the case if only a single spark gaparrangement were employed, and the rate of change of sparking distanceincreases with the number of gaps. Such a rotary gap scheme as isdisclosed herein prevents possible spurious discharges and improves theaccuracy of firing and the speed of disruption. Obviously, the speed ofthe disc is related to the timing of the pulse length.

In the example given above of the production of pulses having a timeduration of one microsecond, it will be apparent that if line TL were astraight line it would require a length of 150 meters. In order toreduce the overall length of this line, it may be coiled, or preferablytake the form of the line of Fig. 1a. The line of Fig. la may occupy aspace of only six feet and give the same results as a straight coaxialline oi 150 meters. More specifically, the line of Fig. 1a, is

composed of a pair of hollow conductors 20 and 2 I ductor, each rodbeing notched to enable a coiled conductor 23 to be Wound around theinner conductor but spaced therefrom by the rods 22. The inner conductor2I reduces the mutual inductance between adjacent turns of the coil, andthe outer conductor 20 serves as a shield which also reduces the mutualinductance between adjacent turns.

Fig. 2 illustrates another embodiment of the invention for producingsharp ultra short wave pulses, The line TL, which is the same as shownin Figs. l and 1a, or any equivalent frequency, is here shown foldedback on itself in order to more clearly indicate that the connectionfrom the magnetron oscillator I to the terminal 8 of the line is veryshort and has no time determining factor. Here again the line TL ischarged through the vresistance 6. However, in this gure one end of theline TL (the inner conductor at terminal l) is directly connected to thespark gap arrangement, whereas the other end of the inner conductor atterminal 8 is connected to the saine spark gap through the loadresistance of the magnetron I. As mentioned in connection with Fig. 1,the spark gap is preferably of the type shown in Fig. 1c, although itmay be a quenched spark gap or an unquenched spark gap. The possibilityof current passing through the oscillator I because of a continuing arcacross the spark gap is avoided in Fig. 2 by virtue of the directconnection I which shunts line TL and the oscillator load I'. Chargingvoltage from source 5 is applied to the inner conductor line TL, asdescribed before in connection with Fig. l. The resistance or impedanceof oscillator I is the same as the characteristic impedance of line TL,and resistance 6 has a value considerably greater than thecharacteristic impedance of line TL.

In the operation of Fig, 2, the following happens when the charge on theline TL is of such value as to cause a discharge across the spark gap.The voltage across terminal 1 becomes zero or near Zero, by virtue ofthe fact that the outer shell of the line is grounded and the innerconductor is connected through line II) to ground through the extremelylow resistance path of the spark gap in its condition of discharge. As aresult of the voltage across 'I becoming zero or near so, a negativewave is initiated at terminal 'I and travels down the line towardterminal 8, andas it goes reduces the line potential by the amount ofthe stored or charged voltage E. At the same time, the potential atterminal 8 drops to a potential half that of the charged or storedpotential, thereby launching from 8 toward terminal I a wave whichreduces the line potential by one-half E as it goes, thereby leaving thepotential at terminal 8 at the value one-half E. When the Zero or shortcircuited wave initiated at terminal I arrives at terminal 8, it reducesthe potential at terminal 8 by the amount E, thus causing the potentialat 8 to become -1/2E, which means that the potential across the loadresistance (magnetron) has been reversed. Since, however, the magnetronI is a rectifying device, this reversal will stop current already:Ilowing through the magnetron. The direct current pulse obtained by themagnetron from the line TL can thus be said to be clipped orextinguished by this phenomenon. At the same 'time and the timeimmediately following this phenomenon, the spark gap current through 3will drop in the same manner as described in connection with Fig. 1.

Fig. 3 illustrates a modication of the system of Fig. 2, and in generalhas a principle of operation very similar thereto. The circuit of Fig, 3illustrates an arrangement whereby the voltage from the charging source5 reverses its effect upon the magnetron I. This feature is sometimesuseful because the rectifier in the direct current charging source 5 ismade to provide a xed polarity with respect to ground, and furthermorebecause it may be desirable to ground one or the other electrons (anodeor cathode) of the magnetron I. In the system of Fig. 3, the chargingsource 5 instead of charging the central conductor of the transmissionline, as in the case of Figs. l and 2, now charges the shell of the sameline, which shell is connected to the spark gap 3. The two connectionsfrom the terminals of center conductor of the line TL instead of goingto the spark gap as in Fig. 2, are now directly connected to oppositesides of the oscillator load I, one of these connections going toground. Although the direct current charging source 5 is here shownconnected to the center of the shell of the line TL, it should beunderstood that it may be connected to any point on the shell of theline, such as at one end. A comparison of Figs. 2 and 3 will show thismain difference: Whereas in Fig. 2 the spark gap is connected to theinner conductor of the line TL and the charging source 5 also connectedto this inner conductor, in Fig. 3 the spark gap is connected to theouter conductor or shell of the line TL and the charging source 5 alsoconnected to this shell. Further, whereas in Fig. 2 the outer conductorof the line TL is grounded, in Fig. 3 the inner conductor of the line TLis grounded at one end.

The same remarks hereinbefore mentioned in connection with the relativevalues of the load resistance of oscillator I and the characteristicimpedence of the transmission line, as well as the value of resistor Ealso apply in the case of Fig. 3.

Fig. 4 illustrates another embodiment of the invention and which avoidsthe use of a high voltage continuous direct current source shown inFigs. l, 2 and 3 (trickle charge method), or the need of a low frequencyinput of high voltage according to known systems.

In Fig. 4 the numeral II represents a rectifier which recties thecurrent from a 400 volt alternating current 60 cycle source and appliesthe saine through an inductance coil I2 to a stationary brush I3associated with a commutator I4. The segments on the commutator areconnected to one electrode of condenser I5, the other electrode of whichis connected to ground and to one terminal of an inductance coil I6. Theother terminal of inductance coil I is connected to a stationary brushI'I. Brushes I3 and I'I are so arranged on commutator I that when onebrush is in contact with a segment, the other brush is resting on aninsulating bar, and vice versa. Inductance I forms one coil of an opencore transformer whose other coil I8 is connected between ground and anelectrode of rectifier tube I9. A transmission line TL of the type shownin Figs. l or la, cr any equivalent structure, is connected between therectier tube I9 and the spark gap arrangement 3. The other side or thespark gap ararngement is connected to the magnetron oscillator load I.By means oi the commutator I3, condenser I5 and transformer arrangementIii7 i3, it is possible to produce a pulse of 26,030 volts which isapplied to the line TL. Putting it in other words, the arrangement ofcircuit elements I4, I5 and I6, together with their asso- 7 ciatedfeatures, .converts the 400" volt charging potential to periodic pulsesof 20,000 volts. The inductance coil l2 serves to tune the condenser l5t the pulse frequency for a more efcient transfer of energy from thesource Il to the line TL; that is, coil l2 tunes condenser l5 not at therepetition rate of the pulses but rather to the time that the contact isclosed in such a way that when the contact opens there is, for themoment, no current to be interrupted. In this way a clean break isobtained Without deleterious arcing. f

The shaft of the commutator i3 is linked to the shaft of the rotaryspark gap 3 and to a single motor M, so that there is a synchronousoperation by means of which the spark gap will be in dischargingposition at the time that the transformer T is inactive. The spark gapis made to discharge at the time that the transformer is inactivebecause the activeperiod of the transformer is much longer than thedesired active period of the spark gap and it is desired to avoid anytrailing effects on the spark gap. For this reason also, the spark gapis made to be operative for a much shorter period of time than theactive period of the transformer. In Fig. 4 the line TL is charged, andits length again determines the length'of the pulse, in substantiallythe same manner as hereinbefore described in connection with Fig. 1.Here again, the impedance or resistance of oscillator l is the same asthe characteristic impedance of line TL.

Figs. 5 and 6 show modifications of the system of Fig. 4. In Fig. 5 thecommutator Hl and associated brushes is replaced by a vibrator orchopper 5D having a suitable rate of operation, preferably synchronizedwith the operation of the rotary gap. In Fig. 6, the switchingperformance is achieved by a vacuum tube 5i whose grid is biased sonegatively by source 52 as to be nonconducting until such time as therotary chopper or positive pulser 53 provides a positive pulse on thegrid of tube 5l of such magnitude as to overcome the negative bias andthus cause the tube to become conductive. The speed of rotation ofchopper 53 -is synchronized with the speed of rotation of rotary gap 3.It will thus be seen that the important concept in Figs, 4, 5 and 6 liesin the use of a condenser which is charged and later discharged throughthe primary of an induction coil.

Figs. 7 and 7a illustrate diagrammatically only a preferred form ofchopper circuit for converting the low direct current voltage in thesystems of Figs. 4, 5 and 6 to periodic pulses of high voltage, thelatter to be impressed upon the rectier tube of the circuits of Figs. 4,5 Vand 6. Fig. 7a is the same circuit as Fig. 7, except that the contactmaking device is shown in more detail as constituting part of arotatable commutator device.

Referring to Fig. 7 in more detail, there is shownV the low directcurrent voltage source il which supplies energy to a'condenser i5, thiscondenser being charged and discharged through the primary winding I6 ofa transformer whose secondary winding I8 delivers periodic high voltagepulses to the rectifier tube (not shown) of the circuits of Figs. 4, 5and 6. Putting it in other words, the arrangement of Fig. '7 can replacethat portion of the circuits of Figs. 4, 5 and 6 immediately to the leftof the rectier tube le. Switches 25 and 25 function simultaneously tochange the position between their respective contacts. Switch 25 hasassociated therewith contacts 2T and 28, whileswitch 26 has associatedtherewith contacts 29 and 3B. `In, the position shown in the drawing ofFig. 7, the condenser l5 is charged from the lovf voltage source I lthrough the primary winding i6 of the transformer. After the condenserE5 is charged, the switches 25 and 26 operate simultaneously to changetheir positions from engagement with contacts 26 and 30, respectively,to contacts 23 and 29, respectively, in which last position thecondenser l5 will discharge v'through primary winding I5. The chargingand discharging of the condenser l5 through primary winding iii willcause current pulses to flow through the induction Coil. The particulararrangement of the switches 25 and 2S assures that the current pulsesthrough the primary I6 are in the same direction, and this is importantbecause the oscillation set up in this circuit is extremely highlydamped, and the output of the secondary winding i8 passes through therectier tube. It will thus be seen that by reversing the connections or"the condenser between each charge, I assure the fact that the currentpulses through the primary winding do not change their direction.v Inthis way a pulse corresponding to twice that or the voltage of thesource Il and always of the same direction passes through the primary ofthe induction coil.

Fig. '7a illustrates in more detail one way of achieving the reversalsof the connections to the condenser l5 between each charge. A rotatingcommutator having a plurality of equally spaced commutator segments 3lserves to achieve this result. The condenser l5 has its upper armatureconnected to a plurality of contacts 32 and 33, while the lower armatureof condenser l5 is connected to a plurality of contacts 34 and 35. Thelow voltage source II is connected to a plurality of contacts 36 and 31,while the upper terminal of the primary winding I6 is connected to aplurality of contacts 38 and 39. In one position of the commutator, onesegment 43| will bridge contacts Si and 32, while at the same timeanother segment 3l will bridge contacts 39 and 35, thus producing acomplete circuit from the charge source H through the condenser l5 andprimary winding l5. It should be noted that in this position there is nodirect connection between contacts 35 and 35, or between contacts 38 and33. In another position of the commutator, a segment 3l will bridgecontacts 36 and 34, while simultaneously another segment 3i will bridgecontacts 38 and 33. At this particular time, there will be no directconnection between contacts 37 and 32 and 39 and 35, by virtue of thefact that the segments which bridged them have now passed beyond thesecontacts in their path of travel. In this last position, the circuitwill again be complete from the low voltage source Il through thecondenser i5 and through the primary winding I6; but, it should benoted, that the connections to the condenser l5 have now been reversedrelative to the iirst position. As the commutator revolves, this cycleof operations will be repeated, thus producing alternate charges anddischarges of the condenser through the primary winding i6 in the samedirection.

One advantage of the chopper circuit of Figs. '7 and '7a is that thecontact device is not subjected to any current breaking and consequentarcing, which may occur in the circuits of Figs. 4, 5 and 6, and againstwhich measures were taken in the circuits of Figs. 4, 5 and 6 by the useof a resonance inductance l2.

It should be understood that my improved chopper circuit shown inFigs.'7Y and 7a is not limited to the particular pulse transmission systemshown in the other figures of the drawings, since this chopper hasapplication to other systems wherever it is desired to use anarrangement for transforming a low voltage direct current to a muchhigher voltage in the form of pulses. In applications of the improvedchopper of the invention to other systems where it may not be importantthat the current pulses from the primary do not change their direction,I can use a simplication of the systems of Figs. 7 and 7a. Thissimplification is shown in Fig. 8 and comprises the use of condenser tpermanently connected in series with inductance coil I6, the armature ofthe condenser furthest away from the inductance coil being connected toa switch 40 which can alternate between two contacts 4i, `42. One ofthese contacts 4I is connected to the low direct current voltage source,while the other Contact 42 is connected to ground. `In this last case,however, the charging and discharging of the condenser l5 as the switch40 alternately engages its contacts il and 42, will cause currentreversals in the primary of the induction coil or transformer.

The term ground used in the specication and claims is deemed to includeany point or surface of xed alternating potential or of zero radiofrequency potential.

It should be understood that the spark gaparrangements described hereinare illustrative of any suitable switching systems.

What is claimed is:

1. A system for producing equal length pulses comprising a source ofcharging voltage, a storing circuit in the formof a line ofpredetermined electrical length, an oscillator whose resistance duringoperation is the same as the characteristic impedance of said line, aconnection from an electrode of said oscillator to one terminal of saidline, a spark gap in said connection, a connection from ground toanother electrode of said oscillator, whereby the now of current throughsaid spark gap polarizes said first electrode to cause said oscillatorto produce oscillations, and a resistance whose value is appreciablygreater than the characteristic impedance of said line connected betweensaid source 0I charging voltage and said line` said spark gap being arotary arrangement having a multiplicity of serially arranged gapsgreater than two.

2. A system for producing equal length pulses comprising a source ofcharging voltage, a storing circuit in the form of a line ofpredetermined electrical length, an oscillator whose resistance duringoperation is the same as the characteristic impedance of said line, aconnection from an electrode of said oscillator to one terminal of saidline, a spark gap in said connection, a connection from ground toanother electrode of said oscillator, whereby the ilow of currentthrough said spark gap polarizes said rst electrode to cause saidoscillator to produce oscillations, and a resistance whose value isappreciably greater than the characteristic impedance of said lineconnected between said source of charging voltage and said line, saidline comprising a coil wound around a hollow conductor but insulatedtherefrom, there being a hollow conductor surrounding said coil andinsulated therefrom and connected at its ends to said other hollowconductor.

3. A system for producing equal length pulses of carrier wave energy,comprising a source of charging voltage, a storing circuit in the formof a compactly arranged line of predetermined electrical length, saidline having a conductor element and a shell element surrounding thesame, a carrier wave generator whose resistance during operation is thesame as the characteristic impedance oi said line, connections from apair of electrodes of said generator to opposite terminals of saidconductor element, a spark gap one terminal oi which is connected toground, a direct connection from the other terminal of said spark gap toone element of said line, and a connection from said charging source tothe same element of said line, the other element of said line beinggrounded, whereby the flow of current through said spark gap caused by acritical value of charge on said line completes a circuit for renderingsaid generator operative.

e. A system for producing equal length pulses oi' carrier wave energycomprising a source of charging voltage, a storing circuit in the formof a compactly arranged line of predetermined electrical length, saidline having a conductor element and a shell element surrounding thesame, a carrier wave generator whose resistance during operation is thesame as the characteristic impedance of said line, connections from apair of electrodes of said generator to opposite terminals of saidconductor element, a spark gap one terminal of which is connected toground, a direct connection from the other terminal o f said spark gapto a terminal of said conductor element oi the line, and a connectionfrom said charging source to the same terminal of said conductor elementof said line, and a connection from ground to said shell, whereby theilow of current through said spark gap caused by a critical value orcharge on said line completes a circuit for rendering said generatoroperative.

5. A system in accordance with claim 3, characterized in this that saidgenerator is a magnetron, and an antenna is coupled to the anode of saidmagnetron.

, 6. A system for producing equal length pulses of carrier wave energycomprising a source of relatively low direct current charging voltage, astoring circuit in the form of a compactly arranged line ofpredetermined electrical length, said line having a conductor elementand a shell element surrounding the same, a carrier wave generator whoseresistance during operation is the same as the characteristic impedanceof said line, connections from a pair of electrodes of said generator toopposite terminals of said conductor element, a spark gap one terminalof which is connected to ground, a direct connection from the otherterminal of said spark gap to one elelnent of said line, and aconnection from said charging source to the same element of said line,the other element of said line being grounded, whereby the low ofcurrent through said spark gap caused by a critical value of charge onsaid line much greater than said charging voltage completes a circuitfor rendering said generator operative.

7. A system for producing equal length pulses of carrier wave energy,comprising a source of relatively low voltage alternating current, meansfor rectifying said alternating current, a commutator having a pair ofbrushes so arranged that when one brush contacts a segment on thecommutator the other is insulated from said commutator segments, andvice versa, a connection including an inductance element between one ofsaid brushes and the output of said rectier, an open core transformerhaving primary and secondary windings, a connection from one point onsaid primary winding to the other brush, and a connection from anotherpoint cn said primary winding to the segments of said commutator througha condenser, a connection from said last point to ground, connectionsfrom separated points on the secondary winding of said transformer toground and to a rectifier circuit, respectively, whereby rotation ofsaid commutator causes said transformer system to translate therectified low voltage applied to said commutator to high Voltage energywhich is rectified by said last rectifier circuit to produce directcurrent pulses, said inductance element having a value which tunes withsaid condenser, a storing circuit in the form of a line ofpredeterminedlength, a connection from one end of said line to the output of saidlast rectier circuit, an oscillator whose resistance during operation isthe same as the characteristic impedance of said line, a connection froman electrode of said oscillator to the other end of said line, a rotaryspark gap in said connection, a connection from ground to anotherelectrode of said oscillator, whereby the flow of current through saidspark gap polarizes said rst electrode to cause said oscillator toproduce oscillations, said spark gap being so constructed and arrangedthat it is operative for a much shorter period of time than the activeperiod of said transformer, and means for synchronously driving saidcommutator and rotary gap, whereby said spark gap is in dischargingposition at the time said transformer is inactive.

8. In a system for producing equal length pulses of carrier wave energy,a source of relatively low voltage alternatingcurrent, means forrectifying said alternating current, a commutator having a pair ofbrushes so arranged that when one brush contacts a segment on thecommutator the other is insulated from said commutator segments, andvice versa, a connection including an inductance element between one ofsaid brushes and the outputof said rectifier, an open core transformerhaving primary and secondary windings, a connection from one point onsaid primary winding to .the other brush, and a connection from anotherpoint on said primary winding to the segments of said commutator througha condenser, a connection from said last point to ground, connectionsfrom separated pointsv on the secondary winding of said transformer toground and toa rectifier circuit, respectively, whereby rotation of saidcommutator causes said transformer system to translate the rectified loWvoltage applied to said commutator to high voltage energy which isrectified by said last rectifier circuit to produce direct currentpulses, said inductance element having a Vvalue which tunes with saidcondenser.

9. In a system for producing equal length pulses of carrier wave energy,a source of relatively low voltage alternating current, means fortranslating said low Voltage current into high voltage current pulses,said means including a condenser and circuit elements for charging saidcondenser from said low voltagesource and circuit connections forperiodically discharging said condenser through the primary of aninduction coil after said condenser has been charged, a rectiiiercoupled to the secondary winding of said induction coil for producinghigh voltage direct current pulses, an oscillator, and means forperiodically applying said high voltage direct current pulses to saidoscillator for exciting the same tov produce interrupted trains ofcarrier wave energy.

10. In a system for producing equal length pulses of carrier waveenergy, a source of relatively low voltage alternating current, meansfor translating said low voltage current into high voltage currentpulses, said means including a condenser and circuit elements forcharging said condenser from said low voltage source and circuitconnections for periodically discharging said condenser through theprimary of an induction coil after said condenser has been charged, arectier coupled to the secondary winding of said induction coil forproducing highV Voltage direct current pulses, an energy storage circuitcoupled to said rectifier and adapted to be charged to a critical value,an oscillator, a path from an electrode of said oscillator to saidenergy storage circuit, whereby said storage circuit discharges throughsaid oscillator upon exceeding said critical value to supply apolarizing potential -to said oscillator, to thereby cause it to produceoscillations.

NILS E, LINDENBLAD.

